Lock for manhole covers



A. MADDOCKS LOCK FOR MANHOLE COVERS Filed March '1, 1924 I I .T .ll l l IIIIIII fiFI W 44 I]! E V (/2 gnomh'v Patented Oct. 20, 1925.

ARTHUR; ivtannocxs, or DENVER, COLORADO.

roerzron Manner-n eovnns.

Application filed March "7, E524. Serial N'o GBWiMQ T 0 all whom away eomem; j p

' Be it known that 1, Anrrfiiiif MADDooKs, a citizeirof the United States, residin at Denver, county of Denver, and State of Colorado, have invented certain new and useful Improvements in Looks" for Manhole Covers; andI do declare the following to be afu'll,'clalgand'exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawings, and to the characters of reference marked thereon, which form a part of this specification.

This invention relates to improvements in manhole covers and has special reference to means for locking the same in place.

In our cities there are a large number of sewers, tunnels and conduits of various kinds, to which access is had through manholes. The manholes are located in the alleys and streets and are closed by strong cast-iron covers that rest on a flange secured to a ring. It frequently happens that the covers are removed. either accidentally or intentionally, with the result that serious accidents happen. Owing to the suction between the surface of the roadway and a pneumatic automobile tire, it sometimes happens that the covers are removed from manholes by any rapidly passing automobile that may pass over them.

It is the object of this invention to produce a simple locking means, with which any manhole cover can be equipped, and

which will positively prevent the cover from Y becoming accidentally removed.

Manholes are usually round openings with sides of brick or concrete, to the top of which is secured a cast-iron ring having an inwardly extending flange upon which the cover rests. My invention, briefly described, consists in providing the cover with two diametrically arranged sliding locking bolts whose ends are adapted to engage underneath the flange, and which are held in looking position by a pin which also serves as the means for moving the bolts to unlocking position.

My invention can be most clearly described and will be most readily understood when reference is had to the accompanying drawing in which the preferred embodiment thereof is shown, and in which:

Fig. 1 is a top plan view of a manhole with my cover in place thereon;

Fig. 2 is a sectiontaken on line 2 -2. Fi": 1-; i p ig. 3 isa section also taken on line "22,' and shows the arts to a larger cale; and Fig.4 is abottom planyiew of the'p'arts shew-11' iI I'F'igQ3; 1

The upper ends 'of' the manlio'lesare use: any reinforced *by means of east-iron sings having a cylindrical portion 1 and an outwardly projecting circular flange 2. Projecting inwardly from the inner surface of the cylindrical member is a flange 3 which serves as the support for the cover 4;. The cover has secured to the underside thereof two locking bolts 5. These bolts have slots 6 for the reception of the rivets 7 and are spaced from the bottom of the cover by spaces 8. These bolts can be moved out wardly to the position shown in Figs. 2, 8 and 4 in which position their ends project over the flange 3 and lock the cover in place. When the cover is to be removed, the bolts are moved towards the center a suflicient distance to permit the outer end to clear the inner edge of the flange 3. The cover is providedat its center with an opening for the reception of the tapering pin 9. This pin has a conical head 10 which normally rests in the correspondingly shaped opening. When the pin is in place in the manner shown in the drawings, it holds the bolts in their outward or locking position. When the cover is to be removed, the pin 9 is removed by the aid of a suitable tool which engages the slot 11. After the pin has been removed, the sharp end thereof is inserted into the hole 12 in the end of the bolt and the latter is moved to unlocking position.

In unlocking the cover, it is necessary to move one bolt only to unlocking position, as, the cover can then be raised on one side a sufficient amount to release the same. I have, however, provided two bolts for the reason that in case one becomes frozen or rusted in place so that it cannot be moved, the other will, in all probability, be operable. WVhen the cover is put into place the pin 9 is forced down between the adjacent ends of the locking bolts. This forces the bolts outwardly into locking position so that whenever the pin is in place, the cover is sure to be locked. The pin 9 has a flat head whose upper surface is normally below the surface of the cover and this makes it very diflicult, if not impossible, to remove by unauthorized persons. The head of the bolt has a transverse dovetail slot ll'that can be engaged by a proper tool when the bolt is to be removed.

From the above, it is evident that I have provided a manhole cover with locking means that is simple in its operation, positive in its action, and which'can be readily applied to existing covers.

Having now described my invention, what I claim as new is: p

A circular manhole cover having a substantially flat lower surface, a pair of guide members located on each side of the center in a line passing through the center of the cover, said members projecting downwardly from the lower side of the cover, a locking bolt associated with each pair of guide members, said bolts having a slot for each guide member, said cover having a central opening for the reception of a pointed tapering locking pin which is adapted to be inserted between the adjacent ends of the locking bolts for the purpose of moving them into locking position, one of, said bolts having an opening near its end for'the reception of the point of the tapering pin whereby the bolt may be retracted from looking to unlocking position. 7

In testimony whereof I aflix my signature.

ARTHUR MADDOCKS. 

